Tiny pieces of plastic are aggregating hundreds of miles offshore in concentrations equivalent to those in the "Great Pacific Garbage Patch," according to a Science study. Oceanographer and study author Kara Lavender Law talks about the new questions the study raises.

IRA FLATOW, host:

You're listening to SCIENCE FRIDAY from NPR. I'm Ira Flatow.

You've heard of the Great Pacific Garbage Dump. Let me introduce you to its cousin in the Atlantic. For over 20 years, students participating in what's called SEA Semester have towed nets throughout the Atlantic collecting tiny pieces of plastic and counting them by hand. And they have found that a few hundred miles off the coast of Georgia, there are concentrations of plastic as high as those in the Great Pacific Garbage Patch.

The researchers also found that despite the rise in garbage, the plastic count in the sea has not gone up. So where's all the plastic going?

Kara Lavender Law is an oceanography faculty scientist at the Sea Education Association in Woods Hole and author on this week's study published in Science. She joins us by phone from Geneseo, New York.

And if you want to see a video from an SEA cruise, go to our website at sciencefriday.com. We have it up there on the left side in our Video Pick of the Week spot.

FLATOW: Tell us, how did you did you know about this there all the time? Is it well-known or just kept secret among scientists or what?

Ms. LAW: Well, I would say it's probably been kept secret by SEA Education Association for about 20 or 30 years. For about 40 years, we've been taking students to sea in the Atlantic, and as part of our SEA Semester program, students design scientific research projects that they carry out on board our sailing research vessels.

So in support of those student research projects, we've been towing these plankton nets on the sea surface. And as early as the late 1970s, we began noticing little bits of plastic coming up in the nets, as well.

So we've been collecting these data since then and just recently decided that the time was right to publish them.

FLATOW: So if I go there, am I going to see just, like, you know, a garbage dump full of plastic?

Ms. LAW: No, and that's actually a common misperception about these so-called garbage patches. Really, if I just put you on a ship in the middle of the Atlantic or the Pacific, you really wouldn't see anything, even when you were in the middle of this high-concentration zone.

Most of the bits of plastic that we collect are millimeters in size. So these are smaller than your pinky fingernail, and really you have to tow a net through a large portion of water to even collect them. So they're nothing that you can really see by eye.

FLATOW: And why do they pick the coast of Georgia to show up?

(Soundbite of laughter)

Ms. LAW: Well, they actually don't pick the coast of Georgia. They decide to go far offshore. So it makes them even more difficult to find. But really, the answer to that is the surface currents of the ocean, and this is one of the major points of our work is that we have been able to use just basic ocean physics to explain why the plastic accumulates in this region.

And the short of the answer is that surface currents come together in a region about the latitude of Atlanta but pretty far offshore. So anything floating with those surface currents, including plastic debris or any other kind of natural debris, is likely to concentrate there.

FLATOW: And the mystery, if we're using more plastics, why aren't we seeing more plastic showing up? Where's it going? Where's all the plastic going?

Ms. LAW: That is the million-dollar question. You know, we can't directly measure the amount of plastic that's entering the ocean. So we've used these records of global plastic production and municipal solid waste records from the U.S. to infer that more plastic is entering the ocean. We feel that if people are using more plastic and disposing of more plastic, it's likely that more plastic is going into the ocean.

But in our records, we're collecting plastics just at the very surface of the ocean, and we haven't been able to account for an increase over this 20-year period.

So we think there are a few reasons why this may be. First of all, the mesh size on the net is about a third of a millimeter in size. So we're only collecting pieces that are larger than that. And we know that the effects of UV radiation and wave action on these pieces can break them down into pieces smaller than our net size. So we could be missing a fraction that's still floating at the ocean surface, for example.

FLATOW: And all of this is done by undergraduate students.

Ms. LAW: It is.

FLATOW: It's their summer project?

Ms. LAW: Not summer. We actually do academic programs year-round. So students come out with us for six weeks at a time, and we routinely tow these nets twice a day at the surface. And the students go through the contents of the net to look at the different biological communities, and one of the tasks is to take tweezers and individually pick out these pieces of plastic.

So we've had many undergraduates work on this as their project for their SEA semester. But obviously, it's had a much greater impact, and I think that's really something important to point out.

And another point on this is that our students are not always science majors. They are humanities majors, arts majors. And so these are folks who certainly, most of whom have probably not gone on to become professional scientists, who have made a huge impact.

FLATOW: But they'll keep those tweezers with them the rest of their lives, so...

Ms. LAW: That's right. I'm sure they have fond memories, now that they see this in print.

FLATOW: All right. I wanted to thank you for taking time to be with us. And good luck to you.

Ms. LAW: Thanks very much.

FLATOW: Thanks for coming on. Kara Lavender Law is an oceanography faculty student at the Sea Education Association in Woods Hole and author of this week's study, published in Science. And she was on the SEA cruise. And if you want to see that SEA cruise, you can go to our website at sciencefriday.com.

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